V1057 Cygni

V1057 Cygni is a young stellar object known as a FUOR or FU Orionis variable. These stars are still in the process of forming, accreting gas from the clouds they formed from. FUORs undergo irregular episodes of brightening lasting for several years that are believed to be caused by temporary episodes of higher-than-normal mass accretion. The larger accretion rate results in a larger increase in brightness when the gravitational energy of infalling material is converted to heat; more accretion means more energy released. This star in particular shows some particularly interesting phenomenon, including a dramatic and rapid drop in brightness in mid-1995 (around JD 2449900). This suspicious looking drop wasn't caused by a change in the comparison star sequence, but is in fact quite real (see M.A. Ibrahimov, IBVS 4285). It appears the star underwent a further slight dimming a few years later, and has been slowly oscillating around m(vis)=13.0 since the late 1990s.